However, most cancer is sporadic (meaning that a person does not usually inherit a genetic predisposition that makes them more susceptible to cancer)

In about 5-10% of breast cancers, the woman has inherited a single predisposing gene for breast cancer and we call this hereditary breast cancer.

Although LCIS increases risk for breast cancer in an individual, it is not related to hereditary breast cancer and does not increase your risk of having inherited a mutation in one of the predisposing genes

The two known genes that account for most hereditary breast cancer are BRCA1 and BRCA2

These genes act like brakes on a car and help tell the cell when to stop dividing

If there are changes in these genes it is like the brakes of a car went out and the cell can continue to divide and may lead to cancer

In families that have a mutation in one of these genes we see a number of characteristics that are clues that there is a hereditary cancer

These include-(show visual aid)

Based on family history we can calculate the chance of having a BRCA mutation, but we don't use LCIS in the calculation because it is not associated with an increased risk for these mutations. (We only use individuals with invasive cancer in the risk assessment)

Even in families that have a couple of these clues their chance of having a mutation in BRCA1 or BRCA2 can still be quite low

For instance, I saw a patient last week with breast cancer dx in her 40's and her mother and maternal grandmother had breast cancer in their 60's, but their chance of having a mutation was only around 10%

These families, if they do not have a mutation found, are more likely to fall into a category called familial breast cancer (where we see more breast cancer than expected by chance which is probably due to a number of factors, but these factors are unknown at this time)